Well, I'd say the officers involved in the shooting are at fault here. At the minimum, they failed to follow their own policy.
The police department's policy on shooting at moving vehicles states: "Police officers shall not discharge their firearms at or from a moving vehicle unless deadly force is being used against the police officers or another person present, by means other than a moving vehicle."
But I can also see why the cops would think themselves in danger and defending themselves by shooting since one cop got run over, their van got hit, and the car wasn't exactly stopping (although I probably wouldn't think of stopping if unknown strangers were shooting at me).
The one guy who emptied 2 magazines went totally overboard IMO, but not as bad as some make it out to be, since 2 mags can be emptied in a minute or so. 50 rounds isn't that much either if it was 5 officers shooting. Police issue 9mm magazines probably holds anywhere from 15-20 rounds. So if that one guy emptied 2 mags, then half or more of the shots were his.
Cops also have a revenge mentality when one of their own is hurt/killed (unless that's all in the movies, lol). It's likely the cops all saw the car try to run over one of them and opened fire automatically. Someone's head/s need to roll though, although I'm not all too sure what firing the comissioner is going to solve.